ns2.vultr.com has no NS records.
NS records for this zone are defined at vultr.com.
NS records for this zone are defined at vultr.com.
Question and response
Question
dig ns2.vultr.com. NS
Answer
The response has no answer records.
Authority
vultr.com. 300 SOA ns1.choopadns.com. abuse.choopa.com. 0 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0